Word Doesn't really allow you to do that...
But you can try some tricks to get close to what you want like using text boxes so you can place them where you want people to write and drop some dummy text in it so they know where they should be writing.
For an image on the background non-selectable I usually do this:
Make an image (say A4 / the size your document will be).
Export it as a Jpeg
In word use the Insert menu and choose header [blank]
Drop your jpeg inside the header section.
After this you need to format the position of the image so you can move it freely as your layout requires.
Go to Picture Format and follow these instructions below for positioning options
Choose behind text
position the image as you want and then close the header
After closing the header the image will dim down its opacity.
Just make sure you don't forget that when you print a document the opacity will be 100%. Word just does that so you know that object is not on edit mode.
Like I said, its not ideal and technically anyone can edit the background of the document but it is not very often that people go and edit the header of documents and I usually ask them not to open header or footer when I have to deal with these kind of documents.